a) Field of the Invention
The present invention relates to a disc drive motor having a structure wherein a disc is mounted on a hub and the disc is fixed by a clamper, whereupon the disc is rotated.
b) Description of the Related Art
A disc drive motor for rotating an information recording medium is used in an electronic device such as, for example, a hard disc drive device. Such an electronic device has the following structure. That is, a plurality of discs having information recorded therein are stacked onto a hub with a prescribed space provided between them. Such discs are fixed by means of a clamper, and the hub and the discs are rotated by the disc drive motor. Meanwhile, a magnetic head is disposed facing a recorded surface of the disc. This magnetic head is positioned over a designated track of the relevant disc by a carriage on which it is loaded to thereby write or read information into or from the disc.
The basic structure of the above-mentioned conventional disc drive motor is disclosed in U.S. Pat. No. 4,965,476.
In U.S. Pat. No. 4,965,476, FIG. 3, the outer ring 130 of the ball bearing 126, is fitted and fixed to an inner peripheral surface of the inside opening of the hub 134 and the cap 150 is fixed to the hub 134 in such a manner as to cover one open end of the inside opening of the hub 134. Namely, the cap 150 closes a space located on the upper side of the fixed shaft 112. Accordingly, the space becomes a completely closed space as a result of the use of the cap 150, whereby splashing of the oil mist is prevented. As a result, substances doing harm to the discs such as oil mist which are generated from inside the ball bearing are checked and thus are effectively prevented from splashing upward, whereby the disc drive motor can have high reliability.
In the disclosure of U.S. Pat. No. 4,965,476, FIG. 3, on the hub 134 of the above-mentioned disc drive motor, there are mounted discs 1401, 1402 such as magnetic discs together with spacers 141 interposed between them so that the discs 1401, 1402 are sequentially stacked upward from the flange portion of the hub 134. And in order to fix these discs 1401, 1402, the screws are screwed into the screw holes of the upper end surface of the hub 134, and then the discs 1401, 1402 are fixed while being urged with the clamper 142. As mentioned above, the discs 1401, 1402 are reliably fixed to the hub 134 and thus are rotated without disengaging from the rotation of the motor.
When the discs 1401, 1402 are placed on the flange portion of the hub 134 of the above-mentioned disc drive motor and are fixed with the clamper 142, the following problem arises. Namely, since the hub 134 is rotatably supported by the ball bearings 1261 and 1262, the hub 134 is inconveniently rotated when the clamper 142 is to be fastened by the screws. Thus, there is the problem that the fixing operation is very difficult to perform.
As a countermeasure against this, in order to prevent such inconvenient rotation of the hub 134, as illustrated in FIG. 5 herein, jig engagement holes 30 are formed in the upper end surface of the hub 134 separately from the screw holes 19, to thereby prevent the rotation of the hub 134 by engaging a fixing jig, not illustrated, with one of these jig engagement holes 30. Thus, the clamper 142 is fastened by screws in this state.
In this technique, however, it is necessary that the jig engagement holes 30 with which a jig is engaged be formed at least in the upper end surface 23 of the hub 134. Since these holes are formed by cutting, a significant length of work time was needed. This caused an increase in the parts cost of the hub 134.